Refractory products are often utilized as protective layers to protect the vessels that hold and transfer molten metal in metal casting processes such as steel making. For example, refractory products may be utilized as protective layers to protect furnaces ladles, and tundishes. The purpose of the protective layer is to protect the brick, safety lining, and steel shell of the vessel from steel and slag penetration. By inhibiting this penetration, the protective layer prolongs the life of the vessel.
Conventional methods for forming protective layers include installing a granular refractory composition on the interior faces of a metallurgical vessel and heating the granular refractory composition to solidify and form a protective lining.
The problems associated with installing refractory material in metallurgical vessels are well-known. Various methods are currently used with various drawbacks. For instance, according to one method, a protective layer is applied on the internal faces of a metallurgical vessel by spraying a water-based slurry consisting of a mixture of refractory materials, fibers and a binder. Although this method proves satisfactory, it suffers from the disadvantage of covering the internal faces of the metallurgical vessel with a lining containing a considerable quantity of water, which has to be eliminated by a long and costly drying operation. A second known method includes installing a dry refractory lining composition into a space located between the internal faces of the metallurgical vessel and a mandrel placed within the vessel. The mandrel can be equipped with preheating means and valves through which heat can be applied which sets (hardens) the lining composition that has been poured into the space mentioned above.
Past practices for installing the protective layers have the following drawbacks:
1. In the first method, the main drawback is that considerable water is required, thus requiring drying. In addition, this method has the further drawbacks as follows: PA1 2. In the second method, although no water is required, considerable drawbacks still exist as follows:
a. the slurry spraying equipment requires considerable maintenance, PA2 b. the slurry compositions require careful manufacture to meet specifications, and PA2 c. the installation of the slurry is labor intensive and time consuming. PA2 a. the use of manual labor to hand break 50 to 100 lb. bags of granular refractory material, PA2 b. the unsafe method of loading bulk sacks of granular refractory material into a metallurgical vessel, PA2 c. the unsafe method of loading bulk sacks of granular refractory material into a feed hopper to create a reserve and then dispensing the granular refractory material into the metallurgical vessel (i) by a feed chute or funnel or (ii) by a mechanical feeding apparatus, PA2 d. the unsafe method of hanging a bulk sack of granular refractory material that has a special discharge spout sewn into it over the metallurgical vessel to empty the granular refractory material, PA2 e. the unsafe method of hanging bulk containers of granular refractory material with special outlet discharge hoses over the metallurgical vessel to empty the granular refractory material, and PA2 f. the action of filling the gap can cause segregation of coarse and fine particles resulting in weak areas.
The conventional methods are labor intensive and create unsafe working conditions, especially when working under or near overhead hanging loads. The past practices also create a very irritating dusty work environment.
For example, U.S. Pat. No. 5,302,563 to Rumpeltin et al., and U.S. Pat. No. 5,036,029 to Johnson disclose methods for wet spraying a refractory composition to form a lining in a metallurgical vessel.
In an attempt to overcome the disadvantages of installing a dry composition, U.S. Pat. No. 5,176,873 to Daussan et al. discloses a method that involves the use of a movable wall to form a lining on the internal faces of a metallurgical vessel using a dry granular refractory material. The method involves positioning the movable wall into the metallurgical vessel, introducing the granular refractory material between an internal face of the metallurgical vessel and the movable wall, heating the granular refractory material to sinter the internal face, transversely displacing the movable wall, and repeating the above steps until a lining is complete on the internal faces of the metallurgical vessel. Since the lining of Daussan is prepared one portion at a time, different portions of the lining set at different times. This results in the development of seams in the lining. In particular, the device discussed in Daussan does not permit the development of a continuous lining at the corners of the metallurgical vessel and rather results in seams. This is due to the fact that the device needs to be displaced from each wall once the lining against the wall is made and replaced onto the next wall to begin forming the lining against that wall. During this time, the previous wall cools. Once the subsequent wall is formed, a seam is formed at the corner between the previous and the subsequent wall.
There therefore remains a need for better methods and apparatus that are capable of forming a refractory lining on the internal faces of a metallurgical vessel such as a tundish. The aim of the present invention is to overcome the disadvantages of known methods.